Re: Back up emails in Apple Mail on MacBook Pro
We can't guess whether you have a hundred, many hundreds, or thousands of emails to backup.
If there are attachments and you haven't already done so as they arrived, it's often a good idea to save any images to Photos app, documents into named folders in "Documents", etc. for easy access.
Here are a couple of the methods that are possible for emails.
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(1) In Apple Mail you can export mailboxes (folders) ... ie: they save in .mbox format. To access mailboxes (folders) in .mbox format, you can import them back into the Mac.
To do this see how to:
Import or export mailboxes in Mail on Mac - Apple Support
Eg: says:
"Export mailboxes
(1) Go to the Mail app on your Mac.
(2) Select one or more mailboxes, then choose Mailbox > Export Mailbox.
(3) Choose a folder or create a new folder, then click Choose.
(4) Mail exports the mailboxes as .mbox packages.
If you previously exported a mailbox, Mail doesn’t overwrite the existing .mbox file; it creates a new .mbox file, such as My Mailbox 3.mbox."
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(2) If you want each or any separate email(s) to be available to you for viewing immediately at anytime, you can open and export each one in the Mail app
(A) via File > "Export as .pdf" and keep them all in a folder.
or
(B) via File > "Save as" to save as .rtf files you can open with Text Edit
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Resource for MacOS Tahoe:
Mail User Guide for Mac - Apple Support